1. Field of the Invention
The present invention relates to a brake assembly, and more particularly to an improved brake arrangement and method suitable for use on the wheels of model vehicles such as heavy model aircraft and automobiles.
2. Description of Background Art
Well known to the art of braking is a class of brake generally referred to as hydraulic brakes, in that the actuating mechanism is operated by a hydraulic fluid pressure. As disclosed in U.S. Pat. No. 2,466,917 issued on Apr. 12, 1949 to E. Stewart, in brakes of this type it is necessary that the brake blocks be forced against the brake drum with enough force to stop the rotation of the drum which is usually mounted on the wheel of a vehicle, within a predetermined time and with a minimum of lag between the actuation of the brake pedal and the application of the braking force of the brake block on the brake drum. This is accomplished by some sort of an actuator or mechanism for transforming hydraulic pressure into mechanical thrust on the brake blocks. This hydraulic brake is employed for dynamic braking, that is, slowing up a rotating wheel and bringing a wheel to rest. In the brake system of U.S. Pat. No. 2,287,969 issued to R. W. Brown on Jun. 30, 1942, a tubular member is distended or expanded by the force of fluid therein, increasing the size or diameter of the member and forming a chamber therein. This expansion of the tubular annulus forces friction elements into engagement with a friction drum, so that the rotation of the drum is retarded, the torque being resisted through pins which are interlocked with pans and carried by a torque member. Brown '969 states that when landing a large and heavy ship, such as a transport airplane or a military bombing plane, a field of considerable size is required unless means is provided for bringing the heavy ship to a relatively quick stop after it is grounded. Because of the weight of such ships, conventional brake systems are inadequate to arrest the speed in a sufficiently short time to permit the planes to land on small field with safety. To accomplish such a feat, the Brown '969 invention includes a multiplicity of brakes, all operated in unison provided for each wheel so that even the largest ships when so equipped can be quickly brought to rest after landing. Further, Brown suggests that when taxiing the plane on the ground and otherwise controlling its ground movements, the severe braking action afforded by a multiplicity of brakes may be undesirable.
U.S. Pat. No. 3,180,468 issued on Apr. 27, 1965 to J. Sidles et al. discloses a brake mechanism using an expander tube brake. As stated, such brakes have been actuated by an endless annular rubber tube of oblong cross section, commonly called an "expander" tube, which is radially distensible by fluid pressure to press a series of brake shoes against a rotatable braking member such as a brake drum. Typically, an expander tube had been made as a fully closed tube except for a small fluid inlet pipe. Sidles '468 discloses a fluid distensible flexible actuating member formed in a general sheet configuration. Opposing sides of an annular brake shoe channel receive the annular actuating member and brake shoes. Portions of a frame ring form a bottom portion of the channel. The actuating member is then made in the form of a flat endless flexible ring, the circumference of which is slightly shorter than the circumference of the bottom of the brake shoe channel. The frame member further includes a nozzle which is rigidly fastened to a portion of the frame member in a hole which extends through a rib. A fluid actuating system is then adapted for connection to the interior of the actuating member through the nozzle so that the region of the actuating member between its marginal portion and two margins is communicated to a source of fluid pressure thus performing as a typical flexible fluid distensible actuating member for the brake system.
U.S. Pat. No. 2,457,344 issued to H. J. Butler on Dec. 28, 1948 discloses a fluid pressure brake apparatus having friction elements movable radially by distensible means relative to an annular support wherein the brake comprises members interposed between the distensible means and the friction elements. The interposed members have substantially flat portions on which the friction elements are mounted and web portions adapted to transmit pressure to the flat portions from the distensible means. Butler '344 discloses an embodiment applicable to an aircraft wheel comprising a series of separately formed members having a t-shaped cross section. The legs of the members constitute reinforcing webs located in radial slots provided in an annular support of a channel section. The support carries the distensible means in the form of a hollow rubber or metal annulus distensible by fluid under pressure and being attached to a torque disk secured to the permanent hub of the wheel. A spring ring capable of resilient extension circumferentially when the distensible element is inflated allows the series of t-shaped members and braking elements to be expanded radially outward into contact with the brake drum of the wheel, and further affects their withdrawal radially to their inoperative position on deflection of the distensible means.
The landing and ground controlling movements of the heavy aircraft described in the Brown '969 patent carry over to the landing, controlling and stopping of heavy model jet aircraft within the typical landing distances available to the model aircraft pilot. Typical methods of stopping such an aircraft include wheel brakes, spoilers, reverse thrust and drag shoots. Wheel brakes are typical for road vehicles as well as aircraft and depend on their efficiency for converting kinetic energy into heat then dissipating that heat. As described in an article entitled "Stopping," published Summer 1993, in Radio Control Jet International Magazine, and as is well known in the art of heavy aircraft modeling, with aircraft, wheel brakes usually have maximum weight-to-speed constraints. Such constraints show the maximum speed at which the brakes can be squeezed fully on without danger of them burning out and fading away to nothing. Typically they are hydraulically operated and can be put on with sufficient force to lock a wheel if the runway surface is wet. Thus, they are usually protected by anti-skid mechanisms similar to those in modern cars. Problems typically encountered with model aircraft brakes include finding sufficient force to operate them and having enough brake pad area to be able to stop a relatively heavy and fast landing model.
Well known in the art are cable and push rod systems as well as pneumatic control systems. Cable push rod systems employ a cable operated drum and shoe brake typically worked by a cam pulled by the cable when full up-elevator is applied. In a similar way, pneumatics are used to drive the wheel brakes. In addition to wheel brakes, contact brakes are used wherein fitted brakes in the form of pads are squeezed down into the wheel tires. Such contact brakes worked well enough to keep the taxiing speed down to sensible levels but they were not effective enough for stopping on the landing run available. Additionally, wet tires created even more of a problem.